kvm: rename last argument to kvm_get_dirty_log_protect

mainline inclusion
from mainline-v5.0
commit: 8fe65a82
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I66COX
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=linux-5.10.y&id=8fe65a8299f9e1f40cb95308ab7b3c4ad80bf801



--------------------------------

When manual dirty log reprotect will be enabled, kvm_get_dirty_log_protect's
pointer argument will always be false on exit, because no TLB flush is needed
until the manual re-protection operation.  Rename it from "is_dirty" to "flush",
which more accurately tells the caller what they have to do with it.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>